This invention relates to an inner mirror for a vehicle having an antiglare function of a novel system.
An antiglare inner mirror is a mirror which is capable of changing the reflectance and capable of mitigating the glare of the headlight of a succeeding automobile by reducing the reflectance.
In the past, an inner mirror using a prism has generally been employed. In this prior art mirror, as illustrated in FIGS. 2A and 2B, a transparent glass substrate 10 is made of a prism glass having width changing in the vertical direction and a reflecting film 12 is formed on the rear surface thereof. The glass substrate 10 can be inclined by an inclining device. In the daytime, the glass substrate 10 is inclined downwardly as illustrated in FIG. 2A and incident light from the rear of the automobile (i.e., image from the rear) is reflected by the reflecting film 12 and then is led to the driver's visual point 14. In the night, as illustrated in FIG. 2B, the glass substrate 10 is inclined upwardly and incident light from the rear of the automobile is reflected by a surface 10a of the glass substrate 10 and then is led to the driver's visual point 14. The reflectance by the reflecting film 12 is about 80% whereas the reflactance by the glass substrate surface 10a is only about 4% and, therefore, the glare of the incident headlight of a succeeding automobile in the night can be mitigated.
There has been another type of prior art antiglare inner mirror using a liquid crystal or an electrochromic element for continuously changing the reflectance. In this antiglare mirror, a liquid crystal or an electrochromic element is hermetically enclosed between a pair of glass plates and a reflecting film is formed on the rear glass plate. By controlling electric voltage applied to the liquid crystal or electrochromic element, optical transmittance thereof is controlled and the reflectance thereby is varied.
The prism type antiglare inner mirror illustrated in FIG. 2 is simple in construction and therefore is inexpensive but, since the glass substrate 10 is a prism changing in its width, it is difficult to manufacture this mirror in a case where it is formed in a curved surface for widening the visual field.
The antiglare mirror using a liquid crystal or an electrochromic element requires a drive circuit and a control circuit and, therefore, is rather expensive. Besides, since liquid is hermetically enclosed between the pair of glass plates, when a crack is caused in the glass plates due to an automobile crash, there is the danger that scattered glass injures the passenger.
It is an object of the present invention to solve the above described problems of the prior art and provide an antiglare mirror of a novel system which is simple in construction and is easy to form it in a curved surface.